fix(state): one corrupt timestamp row no longer kills sessions list, export or insights

SQLite dynamic typing lets a TEXT cell ('not-a-timestamp'), inf/nan or a
garbage double (8.4e252 salvaged from a damaged page) sit in a REAL
timestamp column. Every reader called datetime.fromtimestamp()/float
arithmetic on the raw cell, so ONE bad row raised TypeError/OverflowError
out of the row loop and took down the whole `hermes sessions list`/browse
table (#102399), all three exporters — JSONL/MD, QMD, HTML (#102352) —
and `hermes insights` (#99959).

Fix the class with ONE helper, hermes_cli.timefmt.coerce_epoch(): a
stored cell becomes float epoch seconds inside a sane 1970..2103 window
or None after a WARNING that names the session id. Every reader routes
through it — relative_time (list/browse/resume picker), format_epoch
(prune/candidates tables), the three exporters' timestamp formatters,
insights' _get_sessions/_day/period range — so a bad row renders as
'?'/'N/A'/raw text for that one cell and the command completes.

Write side: hermes_state_messages._coerce_timestamp (append_message,
append_messages_batch, import) and the import path's started_at now use
the same window, so a new out-of-range timestamp falls back to now()
instead of being persisted — new bad rows cannot be written by Hermes.

Reported-by: #102399, #102352, #99959 reporters; kokhlo's insights
analysis pointed at every reporting site, not just line 860.

hermes_cli/sessions_cmd_browse.py

@@ -58,7 +58,7 @@ def _format_row(s: dict, max_x: int) -> str:
     name = ((s.get("title") or "").strip() or (s.get("preview") or "").strip())[:name_width] or sid
     return (
         f"{name:<{name_width}}  {_session_status_tag(s.get('_status')):<5}  "
-        f"{_msgs_str(s):>5}  {_relative_time(s.get('last_active')):<10}  "
+        f"{_msgs_str(s):>5}  {_relative_time(s.get('last_active'), session_id=s['id']):<10}  "
         f"{s.get('source', '')[:6]:<5} {sid}"
     )
 
@@ -218,7 +218,7 @@ def _fallback_picker(sessions: list) -> Optional[str]:
     for i, s in enumerate(sessions):
         print(
             f"  {i + 1:>3}. {_clip(_label(s), 50):<50}  {_session_status_tag(s.get('_status')):<5}  "
-            f"{_msgs_str(s):>5}  {_relative_time(s.get('last_active')):<10}  {s.get('source', '')[:6]}"
+            f"{_msgs_str(s):>5}  {_relative_time(s.get('last_active'), session_id=s['id']):<10}  {s.get('source', '')[:6]}"
         )
     while True:
         try: